Force sensors are sometimes incorporated into exercise devices for monitoring user activity, e.g., the amount of force applied, the duration of exercise, etc. The force sensors can allow a user (or others, e.g., trainers or physical therapists) to quantify, record, and analyze the user's activity with greater ease and certainty. For example, a sensor might precisely measure and record the amount of weight lifted during one exercise session, as well as the number of times it was lifted, the time over which it was lifted, etc., and the recorded data can then be compared to the results of a later exercise session to determine the user's progress.
Often, the force sensors are built directly into the structures of the exercise devices. (See, e.g., U.S. Pat. Nos. 5,271,416; 6,612,170; 7,510,509; and U.S. Patent Publication 2008/0242509.) In this case, the force sensing functionality suffers from many drawbacks present in the exercise devices themselves. In particular, if the device is dedicated to the performance of only a single particular type of exercise, or a few types of exercises, the user's activity—which will often involve other types of exercise, and thus other exercise devices, as well—may not be fully captured by the force sensor. While a user might have a number of different exercise devices, each bearing its own force sensor for monitoring activities on its particular device, such an arrangement leads to greater expense, and to difficulties with collecting and organizing data from the various devices.
Some sensors are designed to be retrofit into preexisting exercise devices, as exemplified by U.S. Pat. No. 5,538,486 and U.S. Patent Publication 2008/0119763. These devices suffer from the drawback that they are not easily installed in preexisting exercise devices, and moreover tend to be installable in only a limited number and type of exercise device. They also tend to add bulk, restrict range of motion, or otherwise detract from the utility of the exercise devices.
It would therefore be useful to have available inexpensive exercise devices which are capable of accommodating a wide variety of different exercises, and which allow rapid and convenient installation and removal of force sensors for monitoring user activity, wherein the force sensors (when installed) do not interfere with the functionality and usage of the exercise devices.